Zhang Xizhou Cecily, Xue Kai, Salvi Michele, Schomburg Benjamin, Mehrens Jonas, Giller Karin, Stopp Marius, Weisenburger Siegfried, Böning Daniel, Sandoghdar Vahid, Unden Gottfried, Becker Stefan, Andreas Loren B, Griesinger Christian
NMR-based Structural Biology, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany.
Institute for Molecular Physiology (imP), Microbiology and Biotechnology, Johannes Gutenberg University, Mainz, Germany.
Nat Commun. 2025 Jan 22;16(1):935. doi: 10.1038/s41467-024-55671-3.
Membrane bound histidine kinases (HKs) are ubiquitous sensors of extracellular stimuli in bacteria. However, a uniform structural model is still missing for their transmembrane signaling mechanism. Here, we used solid-state NMR in conjunction with crystallography, solution NMR and distance measurements to investigate the transmembrane signaling mechanism of a paradigmatic citrate sensing membrane embedded HK, CitA. Citrate binding in the sensory extracytoplasmic PAS domain (PASp) causes the linker to transmembrane helix 2 (TM2) to adopt a helical conformation. This triggers a piston-like pulling of TM2 and a quaternary structure rearrangement in the cytosolic PAS domain (PASc). Crystal structures of PASc reveal both anti-parallel and parallel dimer conformations. An anti-parallel to parallel transition upon citrate binding agrees with interdimer distances measured in the lipid embedded protein using a site-specific F label in PASc. These data show how Angstrom scale structural changes in the sensor domain are transmitted across the membrane to be converted and amplified into a nm scale shift in the linker to the phosphorylation subdomain of the kinase.
膜结合组氨酸激酶（HKs）是细菌中普遍存在的细胞外刺激传感器。然而，关于其跨膜信号传导机制，仍缺乏统一的结构模型。在此，我们结合晶体学、溶液核磁共振和距离测量技术，利用固态核磁共振来研究典型的嵌入膜中的柠檬酸盐感应HK（CitA）的跨膜信号传导机制。柠檬酸盐与胞外传感PAS结构域（PASp）结合，使连接跨膜螺旋2（TM2）的连接子呈螺旋构象。这触发了TM2类似活塞的拉动以及胞质PAS结构域（PASc）的四级结构重排。PASc的晶体结构揭示了反平行和平行二聚体构象。柠檬酸盐结合后从反平行到平行的转变与在PASc中使用位点特异性F标签在脂质嵌入蛋白中测量的二聚体间距离一致。这些数据表明，传感器结构域中埃级别的结构变化是如何跨膜传递，并转化和放大为连接激酶磷酸化亚结构域的连接子中纳米级别的位移。
